RFID transponders are used for all kinds of identification tasks. They can contain data which is written to or read out by read/write units (R/W-units) in a downlink or uplink data transmission, respectively. The antenna of a RFID transponder is typically built with an inductive loop. This inductor is coupled to a capacitor to form a resonant circuit. During downlink data transmission, the resonant circuit is excited by a radio frequency signal (e.g. 134 kHz). Being subject to the external RF excitation, the resonant circuit starts oscillating. In an uplink data transmission phase, the RFID must perform an oscillation with the resonant circuit, which is then received by the R/W unit. An important characteristic is the maximum reading distance over which data can be safely read. In order to reach large reading distances, the resonant circuit should oscillate exactly at a predetermined frequency. Therefore, resonant circuits of RFID transponders are calibrated in a final stage of the manufacturing line. They are typically based on integrated circuits. The resonant frequency is measured by an external test equipment and based on the test result some trimming capacitors are activated in an integrated circuit (IC) of the RFID transponder. Thereafter, further calibration of the RFID transponder can only be performed with external components. Actually, a second calibration step is practically never performed. The calibration procedure is an important economical aspect of the RFID transponder manufacturing process. It is therefore generally desirable to simplify the calibration process and thereby rendering calibration more flexible.